Time to Lose Weight Calculator

Time to lose pounds/kilos — how it works

Rule of thumb: 7,700 kcal ≈ 1 kg of body fat (≈ 3,500 kcal per pound). A daily deficit of 500 kcal yields about 0.5 kg/week (1 lb/week); 1,000 kcal/day ≈ 1 kg/week. Formula: days = (kg × 7,700) / deficit. Example: 10 kg with a 500 kcal deficit → 10 × 7,700 / 500 = 154 days ≈ 22 weeks. Unit conversion: 1 lb = 0.4536 kg; 1 kg = 2.2046 lb.

• Sustainable pace — 0.5–1% of body mass per week. Deficits above 1,000 kcal/day risk loss of lean mass, micronutrient deficiency and metabolic adaptation.
• Body recomposition — combine modest deficit (300–500 kcal) with resistance training to preserve muscle; the scale moves slower but body composition improves.
• Plateau — the body adapts; weight loss is not linear. Refeeds, diet breaks and recalculating TDEE every 4–6 weeks counter adaptive thermogenesis.
• Unit context — the pound (lb) is British in origin; the US keeps the imperial system, the rest of the world uses SI. Conversion matters for Anglo recipes, gym plates and clinical references.

Brazilian context

In Brazil, nutritionists and CFM (Conselho Federal de Medicina) recommend a maximum loss of about 1 kg/week and supervised follow-up. Crash diets (< 1,000 kcal/day) without medical follow-up are discouraged. Bariatric surgery (NR-7 of CFM) is indicated only above BMI 35 with comorbidities or BMI 40, after failed clinical attempts.

FAQ

Why 7,700 kcal per kilo? Pure fat tissue holds ~9 kcal/g, but body fat includes water and protein, so the practical figure is ~7,700 kcal/kg (≈ 3,500/lb — the classic Wishnofsky number).

How accurate is the estimate? It is a first approximation. Real loss slows as TDEE drops with mass loss; the Hall/NIH model gives a more realistic curve.

Cardio or diet for the deficit? Mostly diet — it is far easier to skip 500 kcal than to burn it. Use exercise for health and muscle, not to "create room" for food.